You won't damage anything unless you seriously overheat it, in which case you can weld pieces of your clutch to the flywheel, which will then absolutely require machining. Like brake rotors, flywheels have thickness limits and can only be resurfaced and seriously overheated so many times before you start getting heat spots and cracking.
You should machine the flywheel anyway when you replace the clutch. Machining brings back the grooves needed to help break in quicker while imbedding a new clutch on the surface. If the flywheel has deep enough surface cracks, the flywheel will need to be replaced.
Or even better replace it with a lightweight item while it's in getting another clutch
